Table 1 Median-scaled relative abundance of rice bran amino acids metabolites with medicinal properties

4-guanidinobutanoate (Rhapontigenin)^a

03464

99.84

194.48

153.27

• Anti-hyperlipidemic

• Antifungal (Candida albicans in vitro)

• Antioxidant (protection against cellular DNA damage caused by intracellular reactive oxygen species (ROS))

(Jo et al. 2014)

(Kim et al. 2013a, b)

(Zhang et al. 2007)

4-hydroxycinnamic acid

02035

3.61

6.62

9.49

• Antioxidant (protective against oxidative damage caused by ROS)

(Shang et al. 2015)

5-oxoproline (Pyroglutamic acid)

00267

10.80

22.81

41.36

• Increases the release of acetylcholine (Ach) and GABA from the cortical surface to improve the age associated memory impairment

(Antonelli et al. 1984)

(Grioli et al. 1990)

3-(4-hydroxyphenyl) lactate

00755

0.35

0.57

1.09

• Antioxidant (decrease the ROS production in neutrophils and mitochondria)

• Antifungal (against main genera: Penicillum, Aspergillus and Fusarium)

(Beloborodova et al. 2012)

(Dallagnol et al. 2011)

α-hydroxyisocaproic acid (Leucic acid)^a

00746

0.16

0.21

0.45

• Antifungal (against Candida and Aspergillus species)

• Antibacterial (broad spectrum bacteriostatic properties)

• Anti-catabolic (inhibitory effect on various matrix metalloproteinase enzymes, which are responsible for degradation of various connective and protein tissues → muscle gaining)

(Sakko et al. 2014)

(Sakko et al. 2012)

(Mero et al. 2010)

Agmatine^a

01432

6.89

0.95

5.23

• Anti-nociceptive (without affecting morphine-induced gastrointestinal transit)

• Anti-hypertensive

• Cancer chemopreventive

• Renal sodium regulation

• Antihyperglycemic (increases insulin release from rat pancreatic islets of Langerhans cells)

(Raasch et al. 2001)

(Piletz et al. 2013)

Betaine

00043

249.03

197.66

308.76

• Protects against atherosclerosis (helps reduce higher levels of homocysteine)

• Prevents hepatic steatosis, prevents cirrhosis (prevents or reduces accumulation of fat in the liver)

• Protects against genetic instability, senescence, and cancer through DNA methylation

(Craig, 2004)

Citrulline

00904

2.72

0.34

ND

• Anti-hypertensive (increases the arginine availability as its precursor and arginine sustains increase in nitrogen oxide (NO) production)

• Anti-hyperlipidemic

(Kaore et al. 2013)

Cystathionine

00099

ND

0.75

1.05

• Anti-inflammatory

(Zhu et al. 2015)

Carboxyethyl-GABA

02201

11.50

12.42

16.56

• Immune modulator

(Cerino et al. 1988)

GABA (Gamma-aminobutyric acid)

00112

163.45

121.42

102.60

• Inhibitory neurotransmitter → Relaxant, anxiolytic and anti-convulsive (antiepileptic)

(Foster and Kemp, 2006)

(Chapouthier and Venault, 2001)

Gentisate^a

00152

ND

0.07

0.27

• Anti-inflammatory (via free radical scavenging)

• Antirheumatic

(Carlin et al. 1985)

(Clarke and Mosher, 1953; Kleinsorge and Pohl, 1953)

Glutamate

00148

777.00

581.99

571.80

• Required for central nervous system function and treating neuropsychological conditions

• Immunomodulator (development of T-cell-mediated immunity by stimulating glutamate-specific receptors)

(Hettema et al. 2006)

(Pacheco et al. 2007)

(Pietersen et al. 1998)

Glutathione, reduced (GSH)

00125

25.76

21.87

14.02

• Antioxidant (as a nucleophile and a reductant, and can react with electrophilic or oxidizing species

(Pompella et al. 2003)

Hydrocinnamic acid

00764

0.07

0.09

ND

• Anti-inflammatory (control of the degranulation of mast cells, basophils and neutrophils)

(Panico et al. 2005)

Indoleacetate^a

00197

1.85

1.73

0.98

• Cancer chemopreventive

(Folkes and Wardman, 2001)

N-Acetyl histidine (NAH)

32055

8.65

11.33

3.36

• Anti-cataract formation (it is one the two major constituents of the vertebrate brain and eye)

(Baslow, 1998; Baslow and Guilfoyle, 2015)

Serotonin

00259

4.71

2.50

14.11

• Neurotransmitter

• Antiemetic

(Peroutka et al. 1981)

(De-Miguel and Trueta, 2005)

N-Acetylserotonin

01238

ND

0.09

0.41

• Anti-insomnia (this is the immediate precursor of melatonin)

• antidepressant & anxiolytic

• Anti-hypertensive

• Antioxidant (lowers resting levels of ROS in peripheral blood lymphocytes, and inhibits nitric oxide synthase)

• Anti-inflammatory

(Touitou, 2001)

(Oxenkrug, 1999; Oxenkrug et al. 2007)

(Reiter et al. 1999)

(Perianayagam et al. 2005)

N-acetylleucine^a

11756

0.12

0.17

0.41

• Vertigo treatment

(Kanchan Rao Singh, 2012; Przybylski, 2008)

N-Acetyl-L-tyrosine

00866

0.10

0.20

0.44

• Treatment of neurotransmitter dysfunction (administration of this amino acid acts as a precursor of catecholamine, dopamine and serotonin)

(M. Hinz, 2003; M. C. Hinz, 2009)

N-acetyltryptophan

13713

ND

0.19

0.55

• Antioxidant (diminishes oxidation of human serum albumin)

• Neuro-protective (Treatment of neurodegenerative disease such as amyotrophic lateral sclerosis)

(Anraku et al. 2004)

(W. Li et al. 2015)

N-methyltyrosine (Metyrosine)

14903

0.06

ND

ND

• Anti-hypertensive (inhibits tyrosine hydroxylase)

(DrugBank; Scriabine et al. 1978)

Norvaline

13716

0.13

ND

0.07

• Anti-inflammatory (via inhibition of ribosomal protein S6 kinase beta-1 (S6K1))

• Improves sperm motility, count and viability in diabetic rats (inhibits the arginase enzyme and increases arginine availability as substrate to interact with endothelial nitric oxide synthase (eNOS))

(Ming et al. 2009)

(De et al. 2016)

Ornithine

03374

1.42

0.12

0.27

• Antifatigue (increases release of human growth hormone by stimulating pituitary gland)

(Sugino et al. 2008)

Phenyllactic acid^a

00779

0.28

0.37

0.59

• Antifungal (against Fusarium graminearum IDM623, Endomyces fibuliger IDM3812, Penicillium expansum IDM/FS2, Aspergillus niger IDM1, and Monilia sitophila IDM/FS5)

• Antibacterial (against Klebsiella oxytoca (g-), Providencia stuartii (g-), Enterococcus faecalis (g+), Staphylococcus aureu (g+) and Listeria monocytogenes (g+))

(Lavermicocca et al. 2000)

(Dieuleveux et al. 1998)

Picolinic acid

02243

0.22

0.66

0.19

• Increases the bioavailability of elements such as zinc, iron, copper, manganese and molybdenum in the human body

• Anti-inflammatory

(Grant et al. 2009)

(Bosco et al. 2000)

Taurine^a

00251

1.41

1.92

1.92

• Antioxidant (found in large quantities in the neutrophil and excitable tissues, is a powerful scavenger of hypochlorous acid)

• Lowers lead and cadmium levels in blood and tissues

• Obesity prevention (increases energy metabolism in white adipose tissue)

• Anti-hypertensive

• Neuroprotective against glutamate excitotoxicity

• Anti-hyperlipidemic

(Christophersen, 2012)

(Gurer et al. 2001)

(Sinha et al. 2008)

(Tsuboyama-Kasaoka et al. 2006)

(Leon et al. 2009)

(El Idrissi et al. 2003)

(Yanagita et al. 2008)

(Huxtable, 1992)

Trans-urocanate (t-Urocanic acid)

00301

0.58

0.77

2.24

• Ultraviolet (UV) protectant (natural sunscreen)

(Egawa et al. 2010)